Alluvion, a word taken from Roman law, is a legal term, describing the increase in the area of land without any act being taken by the owner. The typical cause is sediment (alluvium) deposited by a river. This changes the size of a piece of land (a process called accession) and thus its value over time.
- Chisholm, Hugh, ed. (1911). Encyclopædia Britannica. 1 (11th ed.). Cambridge University Press. p. 710..